root@DietPi:~# journalctl -u adguardhome
-- Journal begins at Sun 2021-10-17 09:49:53 BST, ends at Sun 2021-10-17 10:17:01 BST. --
Oct 17 09:49:55 DietPi systemd[1]: Started AdGuard Home (DietPi).
Oct 17 09:49:57 DietPi AdGuardHome[531]: 2021/10/17 09:49:57.131021 [info] AdGuard Home, version v0.106.3
Oct 17 09:49:57 DietPi AdGuardHome[531]: 2021/10/17 09:49:57.135933 [fatal] couldn't read config file /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: open /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: permission denied
Oct 17 09:49:57 DietPi systemd[1]: adguardhome.service: Main process exited, code=exited, status=1/FAILURE
Oct 17 09:49:57 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:50:02 DietPi systemd[1]: adguardhome.service: Scheduled restart job, restart counter is at 1.
Oct 17 09:50:02 DietPi systemd[1]: Stopped AdGuard Home (DietPi).
Oct 17 09:50:02 DietPi systemd[1]: Started AdGuard Home (DietPi).
Oct 17 09:50:02 DietPi AdGuardHome[691]: 2021/10/17 09:50:02.631158 [info] AdGuard Home, version v0.106.3
Oct 17 09:50:02 DietPi AdGuardHome[691]: 2021/10/17 09:50:02.635309 [fatal] couldn't read config file /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: open /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: permission denied
Oct 17 09:50:02 DietPi systemd[1]: adguardhome.service: Main process exited, code=exited, status=1/FAILURE
Oct 17 09:50:02 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:50:07 DietPi systemd[1]: adguardhome.service: Scheduled restart job, restart counter is at 2.
Oct 17 09:50:07 DietPi systemd[1]: Stopped AdGuard Home (DietPi).
Oct 17 09:50:07 DietPi systemd[1]: Started AdGuard Home (DietPi).
Oct 17 09:50:08 DietPi AdGuardHome[807]: 2021/10/17 09:50:08.161366 [info] AdGuard Home, version v0.106.3
Oct 17 09:50:08 DietPi AdGuardHome[807]: 2021/10/17 09:50:08.178694 [fatal] couldn't read config file /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: open /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: permission denied
Oct 17 09:50:08 DietPi systemd[1]: adguardhome.service: Main process exited, code=exited, status=1/FAILURE
Oct 17 09:50:08 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:50:13 DietPi systemd[1]: adguardhome.service: Scheduled restart job, restart counter is at 3.
Oct 17 09:50:13 DietPi systemd[1]: Stopped AdGuard Home (DietPi).
Oct 17 09:50:13 DietPi systemd[1]: Started AdGuard Home (DietPi).
Oct 17 09:50:13 DietPi AdGuardHome[869]: 2021/10/17 09:50:13.422329 [info] AdGuard Home, version v0.106.3
Oct 17 09:50:13 DietPi AdGuardHome[869]: 2021/10/17 09:50:13.424429 [fatal] couldn't read config file /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: open /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: permission denied
Oct 17 09:50:13 DietPi systemd[1]: adguardhome.service: Main process exited, code=exited, status=1/FAILURE
Oct 17 09:50:13 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:50:18 DietPi systemd[1]: adguardhome.service: Scheduled restart job, restart counter is at 4.
Oct 17 09:50:18 DietPi systemd[1]: Stopped AdGuard Home (DietPi).
Oct 17 09:50:18 DietPi systemd[1]: Started AdGuard Home (DietPi).
Oct 17 09:50:18 DietPi AdGuardHome[938]: 2021/10/17 09:50:18.924888 [info] AdGuard Home, version v0.106.3
Oct 17 09:50:18 DietPi AdGuardHome[938]: 2021/10/17 09:50:18.925784 [fatal] couldn't read config file /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: open /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: permission denied
Oct 17 09:50:18 DietPi systemd[1]: adguardhome.service: Main process exited, code=exited, status=1/FAILURE
Oct 17 09:50:18 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:50:24 DietPi systemd[1]: adguardhome.service: Scheduled restart job, restart counter is at 5.
Oct 17 09:50:24 DietPi systemd[1]: Stopped AdGuard Home (DietPi).
Oct 17 09:50:24 DietPi systemd[1]: adguardhome.service: Start request repeated too quickly.
Oct 17 09:50:24 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:50:24 DietPi systemd[1]: Failed to start AdGuard Home (DietPi).
Oct 17 09:54:03 DietPi systemd[1]: Started AdGuard Home (DietPi).
Oct 17 09:54:03 DietPi AdGuardHome[2937]: 2021/10/17 09:54:03.506925 [info] AdGuard Home, version v0.106.3
Oct 17 09:54:03 DietPi AdGuardHome[2937]: 2021/10/17 09:54:03.508953 [fatal] couldn't read config file /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: open /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: permission denied
Oct 17 09:54:03 DietPi systemd[1]: adguardhome.service: Main process exited, code=exited, status=1/FAILURE
Oct 17 09:54:03 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:54:08 DietPi systemd[1]: adguardhome.service: Scheduled restart job, restart counter is at 1.
Oct 17 09:54:08 DietPi systemd[1]: Stopped AdGuard Home (DietPi).
Oct 17 09:54:08 DietPi systemd[1]: Started AdGuard Home (DietPi).
Oct 17 09:54:08 DietPi AdGuardHome[3015]: 2021/10/17 09:54:08.832123 [info] AdGuard Home, version v0.106.3
Oct 17 09:54:08 DietPi AdGuardHome[3015]: 2021/10/17 09:54:08.834245 [fatal] couldn't read config file /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: open /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: permission denied
Oct 17 09:54:08 DietPi systemd[1]: adguardhome.service: Main process exited, code=exited, status=1/FAILURE
Oct 17 09:54:08 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:54:14 DietPi systemd[1]: adguardhome.service: Scheduled restart job, restart counter is at 2.
Oct 17 09:54:14 DietPi systemd[1]: Stopped AdGuard Home (DietPi).
Oct 17 09:54:14 DietPi systemd[1]: Started AdGuard Home (DietPi).
Oct 17 09:54:14 DietPi AdGuardHome[3088]: 2021/10/17 09:54:14.276328 [info] AdGuard Home, version v0.106.3
Oct 17 09:54:14 DietPi AdGuardHome[3088]: 2021/10/17 09:54:14.278292 [fatal] couldn't read config file /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: open /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: permission denied
Oct 17 09:54:14 DietPi systemd[1]: adguardhome.service: Main process exited, code=exited, status=1/FAILURE
Oct 17 09:54:14 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:54:19 DietPi systemd[1]: adguardhome.service: Scheduled restart job, restart counter is at 3.
Oct 17 09:54:19 DietPi systemd[1]: Stopped AdGuard Home (DietPi).
Oct 17 09:54:19 DietPi systemd[1]: Started AdGuard Home (DietPi).
Oct 17 09:54:19 DietPi AdGuardHome[3143]: 2021/10/17 09:54:19.536830 [info] AdGuard Home, version v0.106.3
Oct 17 09:54:19 DietPi AdGuardHome[3143]: 2021/10/17 09:54:19.537599 [fatal] couldn't read config file /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: open /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: permission denied
Oct 17 09:54:19 DietPi systemd[1]: adguardhome.service: Main process exited, code=exited, status=1/FAILURE
Oct 17 09:54:19 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:54:24 DietPi systemd[1]: adguardhome.service: Scheduled restart job, restart counter is at 4.
Oct 17 09:54:24 DietPi systemd[1]: Stopped AdGuard Home (DietPi).
Oct 17 09:54:24 DietPi systemd[1]: Started AdGuard Home (DietPi).
Oct 17 09:54:24 DietPi AdGuardHome[3150]: 2021/10/17 09:54:24.798827 [info] AdGuard Home, version v0.106.3
Oct 17 09:54:24 DietPi AdGuardHome[3150]: 2021/10/17 09:54:24.800668 [fatal] couldn't read config file /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: open /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome/AdGuardHome.yaml: permission denied
Oct 17 09:54:24 DietPi systemd[1]: adguardhome.service: Main process exited, code=exited, status=1/FAILURE
Oct 17 09:54:24 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:54:29 DietPi systemd[1]: adguardhome.service: Scheduled restart job, restart counter is at 5.
Oct 17 09:54:29 DietPi systemd[1]: Stopped AdGuard Home (DietPi).
Oct 17 09:54:29 DietPi systemd[1]: adguardhome.service: Start request repeated too quickly.
Oct 17 09:54:29 DietPi systemd[1]: adguardhome.service: Failed with result 'exit-code'.
Oct 17 09:54:29 DietPi systemd[1]: Failed to start AdGuard Home (DietPi).
Well you have stored user data on an external disk, right? And it seems AGH has issues to read configuration file due to permission issues. What file system format your external disk has?
Can you share as well following
ls -la /mnt/94BA918FBA916F0C/dietpi_userdata/adguardhome
ok indeed seems to be an issue using a NTFS drive. I will submit a change for next release to have correct permissions even if user data is located on NTFS.